Question

Lucy and her bike together have a mass of 120 kg. She slows down from 4.5 m/s to 3.5 m/s. How much kinetic energy does she lose

Answer 1

Answer:

The kinetic energy of a moving object is given by

K= \frac{1}{2}mv^2K=

2

1

mv

2

where m is the object's mass and v its velocity.

In our problem, the initial kinetic energy is:

K_i = \frac{1}{2} m v_i^2 = \frac{1}{2}(120 kg) (4.5 m/s)^2=1215 JK

i

=

2

1

mv

i

2

=

2

1

(120kg)(4.5m/s)

2

=1215J

while the final kinetic energy is:

K_f = \frac{1}{2}mv_f^2 = \frac{1}{2}(120 kg)(3.5 m/s)^2= 735 JK

f

=

2

1

mv

f

2

=

2

1

(120kg)(3.5m/s)

2

=735J

So, the kinetic energy lost by Lucy and her bike is

\Delta K = K_i - K_f = 1215 J - 735 J = 480 JΔK=K

i

−K

f

=1215J−735J=480J

HOPE IT HELPS ....

Explanation:

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THANKS

Answer 2

The kinetic energy of a moving object is given by

K =1/2 mv²

where m is the object's mass and v its velocity

In our problem, the initial kinetic energy is:

K1=1/2mv1²

   =1/2(120kg)(4.5m/sec²)

   =1215jule

while the final kinetic energy is:

K2=1/2mv2²

    =1/2(120kg)(3.5m/sec²)

    =735jule

So, the kinetic energy lost by Lucy and her bike is

ΔK=K1-K2

   =1215J-735J

ΔK=480jule

Therefore lucy and her bike loses 480jule kinetic energy